1. Field of the Invention
The invention relates generally to communication between devices in a storage application and more specifically relates to improving communication throughput of Serial Advanced Technology Attachment (“SATA”) or Serial Attached SCSI (“SAS”) links.
2. Discussion of Related Art
As applications of information technology have become pervasive in our world, the demand for ever faster data transfer speeds has also skyrocketed. For example, the AT Attachment (“ATA”) standard was initially introduced at 16 MB/s. Recently, the industry has adopted the Serial ATA (“SATA”) standard with an initial signal rate of 1.5 Gbps. A 12 Gbps signal rate is already being planned for Serial Attached SCSI (“SAS”).
However, it has become difficult to beneficially achieve even a signal rate of 3 Gbps. Despite the dramatic increase in signal rates, the materials used for conducting data transfers have remained very much the same. For example, FR4, which is a commonly used printed circuit board (“PCB”) material, is very lossy at 3 Gbps. Even very slight impedance mismatches on a PCB would result in large variations in received signal quality at 3 Gbps.
Large variations in received signal quality at a higher signal rate can in fact result in lowered communication throughput compared to having high signal quality at a lower signal rate. This is because retransmission of data packets, resynchronization/retraining of signals, and/or resetting the communication link can all lower the overall communication throughput. However, although signal quality can be higher at a lower signal rate, there is not a way to effectively achieve higher communication throughput. For example, manual trial and error for achieving higher communication throughput by varying signal rates is not only tedious but is usually impractical in large scale and field applications.
Thus it is an ongoing challenge to improve communication throughput of SATA and SAS links.